Safety trocar with progressive cutting tip guards and gas jet tissue deflector

ABSTRACT

A surgical device for endoscopic surgical procedures capable of preventing injuries to internal organs during insertion. The surgical device can include one or more of the following: a multiple system of sharp blade edges, a mechanical tissue protection device that includes a series of thin plastic guards sliding along the sides of the planar knives and having an angle between their edges smaller than that of the cutting knife edges, one or more fixed conical deflectors to expand the cut tissue passage leaving the guards to contact tissue contact only at their tips, an insufflation passage configured to transport fluid into the body cavity during penetration, a locking system for the guards that prevents accidental reuse of the cutting features, and/or an ergonomic design which facilitates handling.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The current invention relates to a surgical device and, morespecifically, to a surgical device containing one or more designfeatures that allow to the device to be used safely.

2. Discussion of the Background

Most existing trocars used for endoscopic surgical procedures areincapable of truly effective prevention of injuries to internal organsduring insertion and manipulation of the trocar. Despite intensiveefforts to improve present trocar designs, the results are still dismal.Present procedures frequently injure internal organs, and the resultingwounds are sometimes serious or even fatal. The need for safer trocarsis thus imperative, especially given that endoscopic surgical proceduresare likely to become more widespread in the future.

Endoscopic or minimally invasive surgery presents an opportunity toimprove present surgical procedures and instrumentation comparable onlyto the revolutionary effect of the introduction of anesthetics in the19th Century.

Most present day trocars utilize a tip “shield”, or cover, for thecutting edges which is usually deployed immediately after penetration ofthe body cavity has taken place. Such a penetration is fraught withdanger of injury to internal organs. However careful a surgeon may beduring penetration of the body cavity, the resistance to penetrationdrops at the last instant prior to damage to the internal organs. Thissudden drop in the resistance to penetration is called a “plunge effect”and occurs prior to any safety feature deployment. In some trocars, thepenetration is controlled in some fashion, either taking place in smallincrements or under some form of approximate direct observation,estimate, or monitoring. In all cases, however, the designs result inmuch of the piercing tip being inserted to a dangerous depth before anyprotecting devices is deployed. This is perhaps not surprising since,after all, a hole must be made before any protection is deployed.

Since in most cases delicate organs are very close to the inside of theskin layer being pierced, it is advisable to perform the penetrationafter internal cavities have been filled with carbon dioxide to minimizethe danger of accidental injury due to contact with the sharp piercingtip or the cutting edges of the instrument. In most cases, however, theforce required for penetration and the elastic nature of the muscularlayer cause a severe depression at the surgical portal, thereforebringing the penetrating tip of the instrument closer to the internalorgans. In some of those cases, the sudden penetration of the cavitywall and the rapid drop in resistance allow the instrument to bepropelled far deeper than desired or is possible to control.Furthermore, friction between the tissue walls and any protective deviceretards the deployment of the protective device, and an injury almostinevitably occurs.

SUMMARY OF THE INVENTION

Accordingly, one object of this invention is to insure that such eventsbe avoided through a surgical device in which a penetrating tip orcutting edge(s) of the instrument be kept, at all times, sufficientlydistant from delicate tissues. Thus, even under dynamic conditions, theprobability of injury will be reduced.

A further object of this invention is to provide a surgical devicewherein insufflation fluid can be driven into a patient duringpenetration of the body cavity by the surgical device to drive theinternal organs away from the surgical device during penetration. Theinsufflation fluid of the present invention can either be supplied froman external pressurized reservoir, or compressed (and hence gathered)during penetration of the body cavity by the surgical device.

A further object of the invention is to provide a surgical device thatcontains one or more cutting edge that provides low frictional forcesbetween the cutting edge and tissue during penetration of the bodycavity, thus reducing the force needed to drive the surgical device intothe body cavity.

A further object of the invention is to provide a surgical device thatincludes a protective device that deploys while remaining substantiallyout of contact with tissue, thus reducing frictional forces between theprotective device and ensuring a controlled and advantageous deployment.

A further object of the invention is to provide a surgical device thatincludes a protective device such as safety guards, wherein the guardingelements have an apex and the angle subscribed at the apex is smallerthan the angle subscribed by the blades or cutting elements of thesurgical device, thus insuring progressive coverage of the blades orcutting elements during deployment of the protective device.

A further object of this invention is to provide a surgical device witha grip mechanism that allows convenient gripping and twisting of thesurgical device during penetration of the body cavity.

A further object of this invention is to provide a surgical device thatincludes a locking system that prevents accidental reuse of the cuttingelements after the tip has been used.

It is therefor desired that this invention, in general, improve surgicalsafety.

These and other objects of the invention are achieved by a surgicaldevice such as a trocar tissue penetrator including a set of thin planararrow-pointed cutting blades joined at a cutting point coaxial andwithin a hollow cylinder penetrator and having the cutting edgesconverge at a cutting angle at the cutting point. The back outside ofthe set of cutting blades can be fixed to the inside of the hollowcylinder penetrator with the cutting edges fully protruding. The hollowcylinder can have its front end slotted and each segment pointed in atriangular shape and bent to fit between the blades and having its edgessubstantially parallel to the edges of the protruding blades but axiallyrecessed behind such edges to act as a tissue expander to preventcontact between inside moving guards and the outside tissue. The slotsbetween the triangularly shaped bent section tissue expanders at the endof the hollow cylinder penetrator can be wide enough to permit thepassing between them and the sides of the cutting blades of a guardsheet at least as thick as the blades. A set of elongated axially bentsheet guards can be set to slide freely within the space between thesides of the cutting blades and the triangular bent segments of thehollow cylinder and having their frontal end with a tip angle profilesubstantially more acute than the adjacent angle of the blade edges andterminating in a very small dull round tip. The angular frontal edges ofthe bent sheet guards can have shallow angle ends and curving slowlytoward the edges so that at no time their angle exceeds that of theadjacent cutting edges. The elongated bent sheet guards inserted betweenthe cutting blades and the triangularly bent segments of the hollowcylinder can be attached at their opposite end to a stem which is urgedtoward the frontal cutting edges by a coil spring.

The advantageous characteristics of this surgical device include, e.g.,the following:

a multiple system of sharp planar knife edges that practically eliminatelateral friction and provide a reduced resistance to penetration,thereby reducing the penetration “plunge effect” and tissue springback.

a mechanical tissue protection device that includes a series of thinplastic guards sliding along the sides of the planar knives and, in apreferred embodiment, having an angle between their edges smaller thanthat of the cutting knife edges. It can then be shown that, with propercontouring of such plastic guard edges, it is possible to providecomplete guarding between the cutting edges and the surrounding tissuesfrom the very start of the penetration, and to do so in a trulyprogressive manner, without jerks or discontinuities. The progressiveguarding action that results from the smaller angle between the sides ofthe guards than the angle between the edges of the cutting blades allowsthe guards to plunge into the tiny opening made by the cutting tip andinstantly surround it, thereby preventing injury to internal organsduring the most crucial instant of the trocar insertion. Therefore,guarding action takes place in a truly progressive manner in which, asthe cutting blades continue expanding the tiny initial opening, theguards progressively advance keeping the cutting edges constantlycovered outside the penetrating region and isolated from internal organsuntil the penetration is completed and the cannula fully inserted;

one or more fixed conical deflectors to expand the cut tissue passageleaving the guards to contact tissue only at their tips, thus isolatingthe guards from friction against the tissue at the sides of the point ofpenetration. Therefore, as soon as even a minute opening is made at thetip by the cutting blades, the guards instantly plunge into the openingand prevent the blade tips from any contact with internal organs. Thus,using tissue expanders outside the guards prevents friction between theguards and the tissue, which would retard the deployment action. The useof this tissue expander allows the safety device to function withoutrestriction, thereby eliminating one of the major deficiencies ofexisting trocars. In other words, the dynamic response of the guards isinherently much faster than the rate of penetration of the blades. As aresult, cutting edges are never dangerously exposed to, contact withinternal organs, however fast the penetration rate may be;

an insufflation passage configured to transport fluid into the bodycavity during penetration. The insufflation passage can be pressurizedeither using an external reservoir or by compressing gas contained inthe passage during penetration. Once an initial penetration of theepithelium has been made, fluid from the insufflation passage will drivethe internal organs away from the cutting edge(s). In the case of anexternal carbon dioxide gas reservoir, a carbon dioxide gas valve isopened, thereby pressurizing the penetrator tubular body. Under suchpressurization, since the front is enclosed by tissue, the cutting tippenetrates the tissues while the gas is prevented from exhausting, butas soon as the most minute opening starts to appear at the tip, the gasexpands suddenly into the opening and forcibly deflects delicateinternal organs away from the tip of the cutting surface whilesimultaneously the guard tips are forced through the opening by theirspring. The use of a pressurized fluid (or gas) tissue deflector thuscreates an organ-free zone in front of the cutting blade tips at theinstant of the incipient penetration, even before the guard tips plungeinto the opening. It must also be pointed out that a sudden gasexpansion can also aid the deployment of the guards since the flowoccurs between the cutting blades and the conical expanders, preciselywhere guards may be located. It could almost be said that the guards arespit out by the fluid flow. This increases the velocity of theirdeployment and hence the overall safety of the surgical device;

a locking system for the guards, which is located at the proximal end ofthe instrument, prevents accidental reuse of the cutting features afterthe tip has been safely introduced for the first time. The lockingsystem for the trocar guards includes a locking cylinder attached to alocking button supported by a leaf spring and inserted into a socket.The cylinder has a conical tip and a circumferential groove at thebottom and can be depressed by way of the button and engaged by thegroove into a U shaped spring that will hold it down permitting itsliding motion until it comes out of the U shaped spring and is readyfor locking again on its return to the initial position. If a resetaction is desired it is necessary to push hard downward against thelocking button and deliberately reset it for another cycle. Since thelocking button is located deep within a recess at the proximal sectionof the handle, it demands some effort to reach and actuate, and thus itis difficult to accidentally reset.

an ergonomic design which facilitates handling. The proximalhemispherical knob nestles easily into the hollow of the hand while theindex and middle fingers control rotation by gripping the side horns,thereby permitting push, pull, rotation, and tilting in a very naturaland comfortable manner.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same become betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 shows a general view of an example trocar in isometric pictorialform;

FIG. 2 illustrates a partial broken view of the penetrating end of theexample trocar with guards removed to behind the tip knives toillustrate a shape of this embodiment more clearly;

FIG. 3 shows the same end of the example trocar with the guardsinstalled but retracted as when penetration of an example embodimentstarts, and thus, the knife edges are exposed and ready to startcutting;

FIG. 4 shows the tip of the guards protruding ahead of the cutting tipas when the tip had just started to pierce the abdominal cavity;

FIG. 5 shows the tip of the example trocar with the guards fullyextended and covering the knife edges as when completely inside of theabdominal cavity;

FIG. 6 shows the example trocar tip at the moment it approaches the skinlayer, and thus the guard tips are beginning to push against the skinand be retracted into the penetrator;

FIG. 7 illustrates the point when, in an example embodiment, the guardsare completely pushed into the retracted position and the knife tipsstart to cut into the tissue;

FIG. 8 illustrates the point when, in an example embodiment, the knifetips have completed the passage across the tissue and begin to emergeacross the endothelial layer into the abdominal cavity, and thus thetips of the guards begin to push into the incipient opening while aforceful jet of pressurized carbon dioxide gas pushes delicate internaltissues away from the immediate penetration region;

FIG. 9 illustrates the point when, in an example embodiment, the tips ofthe guards have penetrated the opening and prevent any contact betweenthe knife tips and the surrounding internal tissues while the exposedknife edges behind the opening continue the cutting action, and thepressurized carbon dioxide gas expansion continues to hold delicatetissues away from the cutting region;

FIG. 10 illustrates, in an example embodiment, the continuingpenetration, and thus the guards have penetrated almost completely,while behind them the still-exposed edges continue the cutting actionand the passage of gas continues;

FIG. 11 illustrates the point in an example embodiment when thepenetration has been completed. The knife edges are fully covered by theguards and the tissue opening allows for the passage of the cannula andthe insufflation continues until completed and the penetrator assemblycan be removed;

FIG. 12 shows the top view of an example trocar handle with a portionbroken away to show some internal details;

FIG. 13 illustrates a longitudinal section along a vertical plane “A—A”to exhibit most of the internal details of an example trocar handle;

FIG. 14 illustrates a top view of the distal section of an examplehandle with the grasping horns to facilitate manipulation;

FIG. 15 illustrates an end view of the distal section of an examplehandle as seen from the right showing also a partial broken sectiondetail of the flap valve pivot and lever;

FIG. 16 illustrates a partial isometric view of the example lockingmechanism for the guards stem showing some of the elements within theproximal section of the handle as in Section “A—A” on FIG. 13;

FIG. 17 illustrates an exploded view of some of the example elements ofthe guards stem locking mechanism in an example spatial relationship;

FIG. 18 illustrates an example locking mechanism in a locked position;

FIG. 19 illustrates an example locking mechanism having been unlockedand ready for the start of penetration;

FIG. 20 illustrates how pushing the guards against the skin has forcedtheir stem towards the right;

FIG. 21 illustrates a position of the stem where the guards arecompletely retracted and the knife edges fully exposed for cutting;

FIG. 22 illustrates a position of the locking mechanism after the fullrelease of the guards into the abdominal cavity and the locking of theirstem back to its initial position shown in FIG. 18.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views, and moreparticularly to FIG. 1 thereof, wherein a cannula 2 is firmly attachedto a distal section of a handle which is formed from two segments, thedistal one 6 externally containing gripping horns 6 a, insufflationdevice 11, and flap valve lever 12, and a proximal handle section 5 inthe shape of a hemispherical knob to facilitate its pushing with thepalm of the hand. This section also contains a depression 9 with a flatbottom 9 a, and external mechanisms including a button 7 inserted forsliding into a slot 8 to monitor and control the position of safetyguards at the extreme distal end of cannula 2. The safety mechanismsprotruding distally from cannula 2 include conical tissue expanders 4,and safety guards 3 intended to cover a set of knives (not visible inthis FIG. 1). Those are the externally visible features of thisinvention.

FIG. 2 shows details at the penetrating distal end of the trocar. Ahollow outside cylinder 2 is the cannula which is firmly attached to thedistal section of the handle 6 as was described in FIG. 1. Inside of thecannula 2, there is another hollow cylinder 13 which is the penetrator.This is the removable part which is attached to the proximal section ofthe handle 5, and can be removed after the penetration is completed toallow for the introduction of surgical instruments. The cannula 2 hasits distal end beveled as shown by 2 a to facilitate its introductionacross the tissue opening with minimal resistance. The penetrator hollowcylinder 13 has its distal end formed as a plurality of conical segmentexpanders 4 which are spaced by slots 4 a to allow for the protrusion ofpointed flat knives 14 joined at the center of the instrument andresembling thin arrowheads joined at a center. As shown in FIG. 2, theknives are positioned into the penetrator hollow cylinder 13 to a depthshown at 14 a. The knife edges outside the slots 4 a between the conicalsegment expanders protrude a substantial distance to insure adequatecutting. The set of knives is assembled into the penetrator cylinder 13by spot welds 15, or by other similar mechanism. Right behind thecrossing of the knife blades can be seen the plastic guard tips 3 a. InFIG. 2, the guards are shown as removed from the knives so as tofacilitate the understanding of their shapes and relationship to theknives. The subassembly of the guards 3 is part of a support disk 16which in turn is part of the guards hollow stem 17 connecting them to anactuator spring and locking mechanism at the proximal section of thehandle (not shown here). In the real instrument, the guard tips 3 a areinserted around the knife blades which fit into the narrow spaces 3 bbetween the guards. The guards are then assembled by being pushedforward until they protrude between the blade sides and the conicalexpander slots 4 a as can be shown in FIG. 3 below. In FIG. 3, the tipsof the guards are barely visible because the guards are retracted aswhen the trocar is first pushed against the skin.

FIG. 4 shows the tips of the guards 3 a protruding ahead of the tip ofthe knives and covering them. A short distance behind the tips of theguards 3 a the edges of the knives 14 are exposed and capable ofcutting. FIG. 4 shows the configuration of the trocar cutting tip rightafter initiation of the penetration across the abdominal tissue. At thatinstant, the guard tiny tips 3 a plunge across the start of the openingand quickly cover the sharp cutting point while the exposed knife edgescontinue cutting inside the skin until the penetration is complete asshown in FIG. 5. FIG. 5 shows how the front end of the example trocarlooks after the penetration into the abdominal cavity has beencompleted. At that time all edges of the cutting knives are covered bythe fully extended guards and the whole penetrator assembly can bepulled out with the proximal sector of the handle.

As will be shown later, in one embodiment, at the instant when the firstperforation of the abdominal wall was made, a forceful jet of carbondioxide gas issued across the perforation to deflect away any delicateorgans close to the knives tip while simultaneously the guard tipsentered the opening to cover the point of the knife edges.

The operations just described above are a critical part of thisinvention, therefore they will best be described through the sequence offigures from FIG. 6 through to FIG. 11.

FIG. 6 represents the example trocar guard tips 3 a as they begin tocontact the skin layer 20. The internal organs are shown at the leftside as 25. At this instant, the skin outside layer is deflected underthe force of the guard tips which are urged forward by their spring. Asthe trocar is pushed forward, the guards will be forced into thepenetrator 13 and displace the base disk 16 and guard stem 17 toward theright against the force of their spring.

FIG. 7 shows the guards 3 already completely retracted into thepenetrator 13, and the knife edges 14 completely exposed. At thatinstant, the point of the knives begins to cut and penetrate at 21 intothe outside tissue layer. As shown in FIG. 7, the cutting pathway of thecutting tip/knife edge is of a smaller diameter than the inner diameterof the cannula 2 such that the cut made by the blade results in asmaller lumen or bore than that of the cannula. At that time, the carbondioxide gas is allowed to pressurize the inside of the penetrator 13,and while some gas may escape at first, the tissues around the tip willseal the flow until the cutting tip starts to emerge across the internalabdominal wall.

FIG. 8 shows the onset of penetration. At that instant, the cutting tippoint 14 b has made a very minute perforation 23 and, because of thepresence of the guard tips 3 a, there is enough space to allow a fluidflow (shown here as a gas jet 24) to issue out and cause thedisplacement of nearby internal organ tissues 25 a, while simultaneouslythe guard tips 3 a expand the opening urged by their spring pushing at17 and plunge through the perforation effectively covering the cuttingtip 14 b.

FIG. 9 shows the result of the action described above. The gas jet 24continues issuing and driving internal organs 25 a farther away whilethe guard tips 3 a completely enclose the cutting tip 14 b. All dangerto internal tissues has passed. The extremely quick flow of the gas andthe action of the guard tips make the manipulation factors of thistrocar the safest to master easily. The force or speed of thepenetration action are, within reason, almost immaterial.

FIG. 10 shows the penetration process. The cannula 2 is partlyintroduced across the tissue 27 and the guard tips 3 a continueadvancing and protecting the internal tissues from the knife edges whilethe portions of the edges not yet covered by the guards 14 a are seencutting the remainder of the opening ahead of the cannula, and thetissue expanders 4 facilitate penetration by protecting the guards fromtissue friction. At this point of the penetration the flow of carbondioxide gas 24 is fairly unimpeded and performs the insufflation stageof the process, driving internal organs 25 a farther away from thetrocar portal.

FIG. 11 shows the trocar after full insertion and in the last stage ofinsufflation. The knife edges are now fully covered by the guards, andthe cannula 2 is seen fully inserted across the tissue. The insufflationcontinues until completed and then the penetrator 13 is removed to allowthe insertion of surgical instruments across the cannula.

Having described in sequential detail the insertion, guarding, andinsufflation operations, and the mechanical parts that perform them itremains to describe the additional way by which all that isaccomplished. The mechanisms that allow this are located in the handleof the instrument.

FIG. 12 is a top view of the trocar showing some of the external partsas well as a partial broken view of some interior parts. The body of thehandle is made out of plastic and has two main segments. The proximalsegment 5 is designated to fit into the palm of the hand and has aproximal end of hemispherical shape with a depression of arcuate profile9 at the top terminating at a flat surface 9 a where the guard stemcontrols are located. Those controls are recessed into the flatdepression 9 a to prevent unwanted actuation, and include a double slotwith vertical slots 8 and 8 a into which is inserted a button 7 and itsrectangular guiding shank 7 a. The button 7 is capable of vertical andhorizontal movement, the latter movement being limited between arrows 7″and 11″ as will be described later. The proximal segment 5 is assembledas an integral part of the penetrator system. Its distal end 51 formsthe interface between the two segments of the handle.

The distal segment 6 of the handle has two lateral protruding horns 6 bto facilitate its manipulation during penetration and orientation. Thetwo handle segments 5 and 6 are locked together during usage by way of abayonet stud 29 and slot 29 a. During insertion the stud 29 on part 5 isaligned with the slot 29 a on part 6, pushed, and turned clockwise,until the stud locks the two segments firmly, the knob on 5 and thehorns 6 b provide a good grasp for that operation. The slot 29 a has aslant at the transversal direction running slightly away from theinterface 51 so as to insure that the turning-locking motion will assurea firm and stable connection. This will be discussed further inreference to FIG. 14.

The partial broken section at the top left of the distal segment 6 isintended to show the operation of the flap valve 32, which acts as acheck valve in the illustrated embodiment. The valve has a shaft 34pivoted between the upper 6 and lower 6 a portions of the handle and isurged to rotate counterclockwise by a torsional spring 33 located aroundthe shaft 34. The shaft of the flap valve is firmly attached to thevalve and can be rotated from outside the body segment 6 as will beshown later on FIG. 14. An external lock allows the valve to remain openduring desufflation if turned hard to its stop position 32 a shown indotted lines. As shown in the embodiment illustrated in FIG. 12, thevalve has been opened by the insertion of the penetrator 13. In othercases, the valve could be opened for surgical or visualizationinstruments. When left to itself, the valve will turn counterclockwiseand snap shut against the face of seal 35 which serves as face seal forthe valve and lip seal for the penetrator 13. The left end of FIG. 12shows how the cannula 2 is attached to the handle segment 6 by way of aflange 37, and prevented from leaking by an “O” ring 36. In the sameFIG. 12 is shown how the carbon dioxide gas spigot manual valve 11 ismounted at one side of the top of segment 6.

FIG. 13 is a longitudinal vertical cross section along a plane “A—A” toshow the internal details of the handle. As can be noticed, the twosegments of the handle include a top and a bottom part split along ahorizontal plane for fabrication, one becoming 5 and 5 a, and the other6 and 6 a, and after each segment has been fitted with the internalparts at assembly the two halves of each segment are permanently bondedtogether. Each of the two segments is assembled separately since theymust be detached and attached during usage. The penetrator segment isonly used to make the entry portal, but it must be emphasized that it issuch step that involves the greatest risk.

The distal segment made of parts 6 and 6 a houses the cannula 2 and allthe gas infusion and valving. The connection of the cannula to thesegment part 6 was described before. FIG. 13 shows the gas connector orlayer 11 a to which the gas line is affixed. The valve system is bondedvia a conical stem 11 b into a boss on plane 10 so the incoming gasflows in the direction of arrow 30 and pressurizes the space between theinlet and the seal 35 from where it can enter the openings 38 around thepenetrator 13 walls and fill the space between lip seals 40 and 41.Since the lip seals are oriented toward the front the pressure will openlip seal 40 but not lip seal 41 and the gas will fill and pressurize theentire space along the penetrator 13, not being able to escape when thetrocar tip has been inserted into the tissue, however, as soon as thesmallest opening is made by the point of the blades the gas will escapeas a jet and deflect the surrounding internal organs away from the entryportal. Lip seal 40 is intended to prevent back flow from the penetratorin case of accidental opening or leakage across the gas valve during aprocedure. In such a case, the pressurized volume of gas within thepenetrator 13 will suffice to insure the safe deflection of nearbytissues even before the tips of the guards 3 a plunge into the opening.The guards stem 17 is completely sealed at the front by disk 16 andthereby its interior can be at atmospheric pressure, however, since itmust slide back and forth with the guards it must also be supported atthe proximal end and must be guided over a stationary hollow steel stud44 inserted into it to a minimal depth of four diameters. The proximalend of stud 44 is flared to provide fixation between parts 5 and 5 a ofthe proximal hemispherical knob. A hole 56 on the hollow stud 44 servesto provide air passage in and out of the stud when the guards stem movesback and forth acting as a piston pump. The hole 56 should pass throughthe stud and be of a diameter such as not to impede flow and dampen thesliding action of the guards' stem. Compression coil spring 47 mountedaround stud 44 serves to provide the required force to urge the guardsstem in the distal direction. The proximal end of the penetrator outsidecylinder 13 is flared at 43 for fixation onto the proximal handlesegment parts 5 and 5 a. It is also sealed at the front by an “O” ring42 to insure that no leakage of gas would occur even if seal 35 shouldleak: flared tubular assemblies like 43 are not reliable seals.

The proximal handle segment formed by 5 and 5 a is attached to thepenetrator 13 and contains all its functional and control elements. Theguards stem 17 has at its proximal end a shallow cylindrical depressioninto which a thin ring 45 a which is part of leaf spring 45 is affixed.The exact configuration of the locking system to which the spring 45belongs can be seen in FIGS. 16 and 17, and its function in the sequenceof FIGS. 18 through 22. FIG. 17 is an exploded view of some of theelements of the locking system in their proper relationship. Atassembly, the button 7 is inserted across slot 8 on the top surface 9 aon FIG. 13 and the locking cylinder 48, which has a circumferentialgroove 48 a and a conical end 48 c is pushed up along the stem 7 bagainst the bottom of the rectangular guide 7 a thereby assemblingbutton 7 into the slot 8 a. As the assembly continues the lower tip ofstem 7 b is pushed hard against the punched hole 45 d of the leaf springuntil groove 7 c is gripped by the lateral tabs at 45 d and the assemblyof the button is complete. If now the open hollow cylinder 45 a issnapped onto the surface depression at the proximal end of stem 17, thebutton 7 becomes axially fixed to stem 17 and will follow its back andforth motion in response to coil spring 47 and the forces at the tip ofthe guards. FIG. 16 shows the assembly of the U spring 46 to the lowerinside of 5 by the use of screw 50. FIG. 16 does not show button 7 forthe sake of clarity, but it shows flat spring 45 pushing up against thebottom of the U spring 46. If the assembly of the button 7 and thelocking cylinder 48 was shown there, it would be evident that the buttonwould be pushed upwards and the locking cylinder 48 would be forciblyinserted into the round socket 8 b, thereby preventing any motion of theflat spring 45 and the guards stem 17 attached to it by ring 45 a. Thatis the situation depicted on FIG. 13.

FIGS. 18 through 22 describe an operation of an example locking systemin detail, as follows. In the position illustrated in FIG. 18 the systemis locked: the guards stem and the guards cannot move at all since thecylinder 48 is inserted into the round socket 8 b. FIG. 19 shows whathappens when button 7 is pushed down. When that is done the conical end48 c of cylinder 48 opens the U spring 46 and the spring then snapsclose into the groove 48 a thereby disengaging the locking cylinder fromthe round socket 8 b. The system is then unlocked. The trocar is said tobe “armed”, and able to permit the motion of the guards backwards,exposing the cutting blades for penetration of the skin. That is theposition depicted on FIG. 6. The following discussion is directed to theembodiment shown in FIG. 20. The penetrating force against the skinpushes on the guards and the guards stem 17, and the connecting flatspring 45 moves the button 7 proximally. The rectangular slide section 7a enters the space between guides 8 a, and soon afterwards, the lockingcylinder groove 48 a disengages from the open end of the U spring 46,and the spring 45 pushing upwards against the stem groove 7 c forces thetop of the locking cylinder to snap against the underside of the groove8 a. In that position, the locking cylinder 48 is free to continuesliding along the underside of groove 8 a as shown in FIG. 21 until theinitial penetration is made and the force of the coil spring 47 urgesthe guards stem 17 and the flat spring 45 to return the button 7 to itsinitial position, at which time the locking cylinder will pass freelyover the U spring 46 and snap back into the round socket 8 b locking thesystem into the “safe position” where the guards cannot moveaccidentally. FIG. 22 shows the completion of the cycle back to theinitial configuration of FIG. 18.

A quick review of the provided example locking system from the userviewpoint reveals that the operations include “arming” the trocar bypushing down on the button at the top of the handle at position 7′ shownin FIG. 12, until it “snaps” down; then pushing the trocar against theskin and watching or listening to the position of the button as itslides towards 7′ and then “snaps” to its initial position 7′. That willbe the indication of having completed the penetration. If, for anyreason, button 7 were pushed down accidentally, it could be reset to the“safe” condition by merely moving it in the direction to 7′ and thenreleasing it. It should then get snap-locked at a high level in position7′, and could not be moved without first pushing it down.

The details of operation of the example flap valve, its design, andlocking for deflation are seen in FIGS. 14 and 15. FIG. 14 shows the topview of the handle distal segment, previously presented in FIG. 12 as apartial broken section to show the interior details. FIG. 14, however,is intended to show the external operative controls on this segment ofthe handle in the interest of the user. The flap valve lever 12 is shownin the closed position as it should be when the penetrator is removed.The lever is attached to a shaft 34 whose opposite end is attached tothe flap 32 as seen in FIG. 15. The insertion of the internal trocarelements is performed when the top 6 and bottom 6 a of each handlesegment are separated prior to their being bonded along plane 6 d.

FIG. 15, as explained before, is the end view of the example embodimentpreviously illustrated in FIG. 14 as seen from the right side. That ishow the distal segment of the handle will appear when the proximalsegment is removed. The flap valve external lever knob 53 is providedwith a small depression 54 at its bottom to allow it to be held openwhen the depression is forcibly made to engage a small knob 54 aprotruding from the flat surface 10 after the lever has been turned inthe direction of arrow 52. That is the desufflation position of thevalve which allows the surgeon to use both hands to massage theinsufflated region and expel the gas retained by the patient at the endof the procedure. The arc of rotation needed for the lever to engage theprotruding knob 54 a is labeled as 55. This locking position is notreached by the lever when the valve is opened by the insertion of thepenetrator. The locking of the valve has to be done by the forceful anddeliberate action of the surgeon. The small angle 52 shown at thebayonet locking stud 29 refers to the desirable slant for the groove 29so as to insure that the locking force increases sufficiently to preventaccidental loosening between the proximal and the distal segments of thehandle. The elasticity of the locking elements determines the exactangle to be used, which should be somewhere between 2 and 5 degrees toaccount for tolerance errors. The infusion valve 11, its lever 11 c, andits lever connector 11 a are shown on FIG. 14. In FIG. 15, the openingof the valve is indicated by arrow 11 d. FIG. 15 also shows a brokensection of the valve shaft 34, its top “O” ring seal 34 a, and itstorsion spring 33 inserted into a slot in the operating bracket of valve32. In the same FIG. 15, the seal 35 is seen, as well as the frontsurface 51 a of the distal handle segment, which contacts the matingsurface 51 of the proximal segment.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described herein. Inparticular, it is understood that the present invention may be practicedby adoption of aspects of the present invention without adoption of theinvention as a whole.

What is claimed is:
 1. A method of inserting a cannula through a tissueof an individual using a penetrator, a cutting blade and a guard, whichcomprises: shaping the guard so as to have an apex such that an anglesubscribed in the apex of the guard is smaller than an angle subscribedat the cutting blade for progressively covering the cutting blade tipduring deployment of the penetrator; connecting the cutting blade to adistal end portion of the penetrator for cutting the tissue; and movablypositioning the guard within the penetrator for selectably covering andexposing the cutting blade and progressively covering the blade with theguard during deployment of the penetrator.
 2. The method as claimed inclaim 1, which comprises positioning a tissue expander at the distal endof the penetrator for expanding a portion of the tissue cut by thecutting blade.
 3. The method as claimed in claim 1, which comprisesconnecting the penetrator to a handle for manipulating the penetratorduring cutting of the tissue.
 4. The method as claimed in claim 3, whichcomprises providing an insufflation passageway through the penetratorfor discharging a pressurized fluid there through upon penetration ofthe tissue by the cutting blade.
 5. The method according to claim 4,which comprises positioning a check valve between the insufflationpassageway and an exterior of the penetrator for preventing leakage ofthe pressurized fluid from a penetrator.
 6. The method according toclaim 1, which comprises utilizing a locking mechanism for preventingaccidental exposure of the cutting blade.
 7. The method as claimed inclaim 4, wherein said fluid comprises a gas.
 8. The method as claimed inclaim 1, which comprises forming a distal tip portion of the blade so asto be one of substantially dull tip and substantially rounded tip.